StTCTP Positively Regulates StSN2 to Enhance Drought Stress Tolerance in Potato by Scavenging Reactive Oxygen Species

Drought is a negative agronomic effect that can lead to an increase in reactive oxygen species (ROS) levels. Excessive drought can severely alter cell membrane fluidity and permeability, significantly reducing cell viability. The Gibberellic acid-stimulated Arabidopsis (Snakin/GASA) gene family has an important role as antioxidants in inhibiting the accumulation of ROS and improving crop drought resistance. However, the regulatory mechanism of potato StSnakin-2 (StSN2) in response to drought, along with how StSN2 expression is regulated, is not well understood. In this study, we found that StSN2 was induced by drought. Overexpression of StSN2 significantly increased drought tolerance, whereas silencing StSN2 increased sensitivity to drought. Overexpression of StSN2 resulted in higher antioxidant enzyme (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)) activity, and lowered hydrogen peroxide (H2O2) and malondialdehyde (MDA) accumulation during drought stress. Also, overexpression of StSN2 increased the relative water content (RWC) of leaves and reduced the water loss in leaves. We screened the upstream regulatory protein translation-controlled tumor protein (StTCTP) of StSN2 through DNA pull-down combined with mass spectrometry. Yeast one-hybrid (YIH), electrophoretic mobility shift assay (EMSA), and luciferase reporting assay (LUC) indicated that StTCTP binds the StSN2 promoter. Like StSN2, StTCTP was highly expressed in response to drought. Overexpression of StTCTP increased the photosynthetic rate and CAT enzyme activity, and lowered H2O2 and MDA accumulation during drought. Meanwhile, overexpression of StTCTP increased leaf RWC and reduced water loss. Our research strongly suggested that StSN2 effectively cleared ROS and significantly boosted the drought resistance of potatoes. Furthermore, as a transcriptional activator of StSN2, StTCTP, much like StSN2, also enhanced the potato's drought tolerance. The results provided a foundation for the further study of StSN2 regulatory mechanisms under drought stress.

Helicobacter pylori SlyD stabilizes TPT1 via hnRNPK and enhances OCT1-mediated CDX2 transcriptional activation to drive gastric intestinal metaplasia

BACKGROUND

Gastric intestinal metaplasia (GIM) represents an important precancerous lesion in intestinal-type gastric cancer, triggered by persistent Helicobacter pylori (H. pylori) infection. In a previous study, we unveiled SlyD as a novel virulence factor of H. pylori, establishing its role in GIM induction through TPT1. However, the underlying mechanism remains undetermined.

METHODS

Gastric epithelial cells were stimulated with H. pylori 26695, a SlyD inactivated mutant (ΔSlyD), and purified HpSlyD protein, respectively. Real-time qPCR and western blot were subsequently used to assess the expression levels of hnRNPK, TPT1, OCT1, and GIM markers. RNA sequencing was employed to identify differentially expressed genes associated with H. pylori SlyD infection. Protein stability was evaluated using cycloheximide. Molecular interactions were investigated through co-immunoprecipitation, chromatin immunoprecipitation, and dual-luciferase reporter assays. Additionally, molecular docking was utilized to predict TPT1 inhibitors. Immunohistochemistry staining was conducted to validate hnRNPK, TPT1, OCT1, and CDX2 expression in gastric tissue samples from both human and Mongolian gerbils.

RESULTS

H. pylori SlyD upregulates TPT1 and induces the expression of GIM markers through hnRNPK. The interaction between hnRNPK and TPT1 enhances TPT1 protein stability, with H. pylori SlyD intensifying this association. TPT1 promotes the expression of GIM markers mediated via OCT1, which binds to CDX2 promoter region, thereby modulating its transcriptional activity. Dihydroartemisinin has the potential to target TPT1, inhibiting the H. pylori SlyD-induced expression of GIM markers.

CONCLUSIONS

In vitro and in vivo experiments verified that H. pylori SlyD enhances TPT1 stability through hnRNPK, leading to OCT1-mediated transcriptional activation of CDX2 and the initiation of the GIM process. Our study offers novel perspectives on the pathogenesis of H. pylori-related gastric precancerous conditions.

The mRNA of TCTP functions as a sponge to maintain homeostasis of TCTP protein levels in hepatocellular carcinoma

Translationally controlled tumor protein (TCTP) is a highly conserved protein that accumulated in the tumorigenesis of various malignancies. Despite the important role of TCTP protein in tumor progression, the precise function and underlying mechanistic regulation of TCTP mRNA in hepatocellular carcinoma (HCC) remain unclear. In this study, we found that TCTP protein was overexpressed in HCC patients but TCTP mRNA expression levels were reversed. TCTP knockout HCC cells exhibited attenuated abilities of proliferation, migration, and invasion. The knockdown of TCTP by siRNA effectively reduced TCTP mRNA levels but not protein levels in HCC cells. Moreover, although the constitutive knockdown of TCTP inhibited almost 80% of TCTP protein expression levels in tumors of wildtype transgenic mice (TCTP KD/WT), partial restoration of TCTP protein expression was observed in the tumors of heterozygous TCTP mice (TCTP KD/TCTP±). The blockage of mRNA synthesis with ActD stimulated TCTP protein expression in HCC cells. In contrast, combined treatment with ActD and CHX or MG132 treatment alone did not lead to the TCTP protein accumulation in cells. Furthermore, following the introduction of exogenous TCTP in cells and orthotopic HCC tumor models, the endogenous TCTP protein did not change with the recombinational TCTP expression and kept a rather stable level. Dual-luciferase assays revealed that the coding sequence of TCTP mRNA functions as a sponge to regulate the TCTP protein expression. Collectively, our results indicated that the TCTP mRNA and protein formed a closed regulatory circuit and works as a buffering system to keep the homeostasis of TCTP protein levels in HCC.

TCTP participates in hepatic metabolism by regulating gene expression involved in insulin resistance

Translationally controlled tumor protein (TCTP) has various cellular functions and molecular interactions, many related to its growth-promoting and antiapoptotic properties. Recently, TCTP expression was reported to increases in insulin-resistant mice fed with high-fat diet. TCTP is a multifunctional protein, but its role in liver metabolism is unclear. Here, we investigated the function and mechanism of TCTP in HepG2 cells. Knock-down of TCTP led to 287 differentially expressed genes (DEGs) that were highly associated with cellular apoptosis and signal response, TNF and NF-κB signaling pathways, glycolysis/gluconeogenesis, insulin resistance, FoxO and insulin signaling pathways, adipocytokine and AMPK signaling pathways. shTCTP downregulated the expression of the key gluconeogenesis enzyme phosphoenolpyruvate carboxykinase (PCK1). Furthermore, TCTP regulated the alternative splicing of genes enriched in the phospholipid biosynthetic process and glycerophospholipid metabolism. We further showed that shTCTP down-regulated the intracellular levels of triglyceride and total cholesterol. Our results showed that TCTP regulates the liver cell transcriptome at both the transcriptional and alternative splicing levels. The TCTP regulatory network predicts the biological functions of TCTP in glucose and lipid metabolism, and also insulin resistance, which may be associated with liver metabolism and diseases such as nonalcoholic fatty liver disease.

TCTP is Essential for Cell Proliferation and Survival during CNS Development

Translationally controlled tumor-associated protein (TCTP) has been implicated in cell growth, proliferation, and apoptosis through interacting proteins. Although TCTP is expressed abundantly in the mouse brain, little is known regarding its role in the neurogenesis of the nervous system. We used Nestin-cre-driven gene-mutated mice to investigate the function of TCTP in the nervous system. The mice carrying disrupted TCTP in neuronal and glial progenitor cells died at the perinatal stage. The Nestin^Cre/+; TCTP^f/f pups displayed reduced body size at postnatal day 0.5 (P0.5) and a lack of milk in the stomach compared with littermate controls. In addition to decreased cell proliferation, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) and caspase assay revealed that apoptosis was increased in newly committed TCTP-disrupted cells as they migrated away from the ventricular zone. The mechanism may be that the phenotype from specific deletion of TCTP in neural progenitor cells is correlated with the decreased expression of cyclins D2, E2, Mcl-1, Bcl-xL, hax-1, and Octamer-binding transcription factor 4 (Oct4) in conditional knockout mice. Our results demonstrate that TCTP is a critical protein for cell survival during early neuronal and glial differentiation. Thus, enhanced neuronal loss and functional defect in Tuj1 and doublecortin-positive neurons mediated through increased apoptosis and decreased proliferation during central nervous system (CNS) development may contribute to the perinatal death of TCTP mutant mice.

Function of Translationally Controlled Tumor Protein in Organ Growth: Lessons from Drosophila Studies

Regulation of cell growth and proliferation is crucial for development and function of organs in all animals. Genetic defects in growth control can lead to developmental disorders and cancers. Translationally controlled tumor protein (TCTP) is a family of evolutionarily conserved proteins implicated in cancer. Recent studies have revealed multiple roles of TCTP in diverse cellular events, but TCTP functions in vivo are poorly understood in vertebrate systems. We have used Drosophila melanogaster, the fruit fly, as a model organism for genetic dissection of Tctp function. Our studies have shown that Tctp is essential for organ development by regulating growth signaling. Furthermore, it is required for genome stability by promoting DNA repair and chromatin remodeling in the nucleus. Thus, Tctp acts as a multifaceted cytosolic and nuclear factor for regulating organ growth and genome stability. In this chapter, we describe an overview of our findings on Tctp functions in Drosophila and discuss their implications in cancer.

Structural Insights into TCTP and Its Interactions with Ligands and Proteins

The 19-24 kDa Translationally Controlled Tumor Protein (TCTP) is involved in a wide range of molecular interactions with biological and nonbiological partners of various chemical compositions such as proteins, peptides, nucleic acids, carbohydrates, or small molecules. TCTP is therefore an important and versatile binding platform. Many of these protein-protein interactions have been validated, albeit only few received an in-depth structural characterization. In this chapter, we will focus on the structural analysis of TCTP and we will review the available literature regarding its interaction network from a structural perspective.

The Translational Controlled Tumour Protein TCTP: Biological Functions and Regulation

The Translational Controlled Tumour Protein TCTP (gene symbol TPT1, also called P21, P23, Q23, fortilin or histamine-releasing factor, HRF) is a highly conserved protein present in essentially all eukaryotic organisms and involved in many fundamental cell biological and disease processes. It was first discovered about 35 years ago, and it took an extended period of time for its multiple functions to be revealed, and even today we do not yet fully understand all the details. Having witnessed most of this history, in this chapter, I give a brief overview and review the current knowledge on the structure, biological functions, disease involvements and cellular regulation of this protein.TCTP is able to interact with a large number of other proteins and is therefore involved in many core cell biological processes, predominantly in the response to cellular stresses, such as oxidative stress, heat shock, genotoxic stress, imbalance of ion metabolism as well as other conditions. Mechanistically, TCTP acts as an anti-apoptotic protein, and it is involved in DNA-damage repair and in cellular autophagy. Thus, broadly speaking, TCTP can be considered a cytoprotective protein. In addition, TCTP facilitates cell division through stabilising the mitotic spindle and cell growth through modulating growth signalling pathways and through its interaction with the proteosynthetic machinery of the cell. Due to its activities, both as an anti-apoptotic protein and in promoting cell growth and division, TCTP is also essential in the early development of both animals and plants.Apart from its involvement in various biological processes at the cellular level, TCTP can also act as an extracellular protein and as such has been involved in modulating whole-body defence processes, namely in the mammalian immune system. Extracellular TCTP, typically in its dimerised form, is able to induce the release of cytokines and other signalling molecules from various types of immune cells. There are also several examples, where TCTP was shown to be involved in antiviral/antibacterial defence in lower animals. In plants, the protein appears to have a protective effect against phytotoxic stresses, such as flooding, draught, too high or low temperature, salt stress or exposure to heavy metals. The finding for the latter stress condition is corroborated by earlier reports that TCTP levels are considerably up-regulated upon exposure of earthworms to high levels of heavy metals.Given the involvement of TCTP in many biological processes aimed at maintaining cellular or whole-body homeostasis, it is not surprising that dysregulation of TCTP levels may promote a range of disease processes, foremost cancer. Indeed a large body of evidence now supports a role of TCTP in at least the most predominant types of human cancers. Typically, this can be ascribed to both the anti-apoptotic activity of the protein and to its function in promoting cell growth and division. However, TCTP also appears to be involved in the later stages of cancer progression, such as invasion and metastasis. Hence, high TCTP levels in tumour tissues are often associated with a poor patient outcome. Due to its multiple roles in cancer progression, TCTP has been proposed as a potential target for the development of new anti-cancer strategies in recent pilot studies. Apart from its role in cancer, TCTP dysregulation has been reported to contribute to certain processes in the development of diabetes, as well as in diseases associated with the cardiovascular system.Since cellular TCTP levels are highly regulated, e.g. in response to cell stress or to growth signalling, and because deregulation of this protein contributes to many disease processes, a detailed understanding of regulatory processes that impinge on TCTP levels is required. The last section of this chapter summarises our current knowledge on the mechanisms that may be involved in the regulation of TCTP levels. Essentially, expression of the TPT1 gene is regulated at both the transcriptional and the translational level, the latter being particularly advantageous when a rapid adjustment of cellular TCTP levels is required, for example in cell stress responses. Other regulatory mechanisms, such as protein stability regulation, may also contribute to the regulation of overall TCTP levels.

Current Understanding of the TCTP Interactome

Evolutionarily conserved and pleiotropic, the translationally controlled tumor protein (TCTP) is a housekeeping protein present in eukaryotic organisms. It plays an important role in regulating many fundamental processes, such as cell proliferation, cell death, immune responses, and apoptosis. As a result of the pioneer work by Adam Telerman and Robert Amson, the critical role of TCTP in tumor reversion was revealed. Moreover, TCTP has emerged as a regulator of cell fate determination and a promising therapeutic target for cancers. The multifaceted action of TCTP depends on its ability to interact with different proteins. Through this interaction network, TCTP regulates diverse physiological and pathological processes in a context-dependent manner. Complete mapping of the entire sets of TCTP protein interactions (interactome) is essential to understand its various cellular functions and to lay the foundation for the rational design of TCTP-based therapeutic approaches. So far, the global profiling of the interacting partners of TCTP has rarely been performed, but many interactions have been identified in small-scale studies in a specific biological system. This chapter, based on information from protein interaction databases and the literature, illustrates current knowledge of the TCTP interactome.

Translationally-controlled tumor protein activates the transcription of Oct-4 in kidney-derived stem cells

The molecular mechanisms underlying translationally-controlled tumor protein (TCTP) in the activation of octamer-binding transcription factor 4 (Oct-4) in kidney-derived stem cells have not been characterized. The aim of the present study was to identify the transcriptional activation of Oct-4 by TCTP in kidney-derived stem cells. Homology-directed repair cDNA inserted into Fisher 344 transgenic (Tg) rats and the mouse strain 129/Svj were used for the experiments. Diphtheria toxin (DT; 10 ng/kg) injected into the Tg rats created the kidney injury, which was rapidly restored by the activation of kidney-derived stem cells. Kidney-derived stem cells were isolated from the DT-injured Tg rats using cell culture techniques. The co-expression of Oct-4 and TCTP were observed in the isolated kidney-derived stem cells. Immunoblotting and reverse transcription-polymerase chain reaction analysis of TCTP null mutant (TCTP^-/^-) embryos at day 9.5 (E9.5) demonstrated the absence of co-expression of Oct-4 and TCTP, but expression of paired box-2 was detected. This was in contrast with the E9.5 control embryos, which expressed all three proteins. In conclusion, the results of the present study demonstrated that TCTP activates the transcription of Oct-4 in kidney-derived stem cells, as TCTP^-/^- embryos exhibited knock down of TCTP and Oct-4 without disturbing the expression of Pax-2 The characteristics and functional nature of TCTP in association with Oct-4 in kidney-derived stem cells was identified.

Antagonistic roles of Drosophila Tctp and Brahma in chromatin remodelling and stabilizing repeated sequences

Genome stability is essential for all organisms. Translationally controlled tumour protein (TCTP) is a conserved protein associated with cancers. TCTP is involved in multiple intracellular functions, but its role in transcription and genome stability is poorly understood. Here, we demonstrate new functions of Drosophila TCTP (Tctp) in transcription and the stability of repeated sequences (rDNA and pericentromeric heterochromatin). Tctp binds Brahma (Brm) chromatin remodeler to negatively modulate its activity. Tctp mutants show abnormally high levels of transcription in a large set of genes and transposons. These defects are ameliorated by brm mutations. Furthermore, Tctp promotes the stability of repeated sequences by opposing the Brm function. Additional regulation of pericentromeric heterochromatin by Tctp is mediated by su(var)3-9 transcriptional regulation. Altogether, Tctp regulates transcription and the stability of repeated sequences by antagonizing excess Brm activity. This study provides insights into broader nuclear TCTP functions for the maintenance of genome stability.

Genome stability is important for normal cellular function. Here, Hong and Choi show that translationally controlled tumour protein (TCTP) in Drosophila regulates pericentromeric chromatin remodelling and transcription via negatively regulating a chromatin remodeler Brahma.

Characterization of the Translationally Controlled Tumor Protein (TCTP) Interactome Reveals Novel Binding Partners in Human Cancer Cells

Translationally controlled tumor protein (TCTP) is a highly conserved housekeeping protein present in eukaryotic organisms. It is involved in regulating many fundamental processes and plays a critical role in tumor reversion and tumorigenesis. Increasing evidence suggests that TCTP plays a role in the regulation of cell fate determination and is a promising therapeutic target for cancer. To decipher the exact mechanisms by which TCTP functions and how all these functions are integrated, we analyzed the interactome of TCTP in HeLa cells by coimmunoprecipitation (IP) and mass spectrometry (MS). A total of 98 proteins were identified. We confirmed the in vitro and in vivo association of TCTP with six of the identified binding proteins using reciprocal IP and bimolecular fluorescence complementation (BiFC) analysis, respectively. Moreover, TCTP interacted with Y-box-binding protein 1 (YBX1), and their interaction was localized to the N-terminal region of TCTP and the 1-129 amino acid (aa) residues of YBX1. The YBX1 protein plays an important role in cell proliferation, RNA splicing, DNA repair, drug resistance, and stress response to extracellular signals. These data suggest that the interaction of TCTP with YBX1 might cooperate or coordinate their functions in the control of diverse regulatory pathways in cancer cells. Taken together, our results not only reveal a large number of TCTP-associated proteins that possess pleiotropic functions, but also provide novel insights into the molecular mechanisms of TCTP in tumorigenesis.

The C-terminal cysteine of turbot Scophthalmus maximus translationally controlled tumour protein plays a key role in antioxidation and growth-promoting functions

The translationally controlled tumour protein (TCTP) of turbot Scophthalmus maximus (SmTCTP) contains only one cysteine (Cys¹⁷⁰) at the C-terminal end. The biological role of this C-terminal Cys¹⁷⁰ in the antioxidation and growth-promoting functions of SmTCTP was examined by site-directed mutation of C170A (Cys¹⁷⁰ →Ala¹⁷⁰). It was found that C170A mutation not only obviously decreased the antioxidation capacity of the mutant-smtctp-transformed bacteria exposed to 0·22 mM hydrogen peroxide, but also significantly interrupted the normal growth and survival of the mutant-smtctp-transformed bacteria and flounder Paralichthys olivaceus gill (FG) cells, indicating a key role played by Cys¹⁷⁰ in the antioxidation and growth-promoting functions of SmTCTP. This study also suggested that the self-dimerization or dimerization with other interacting proteins is critical to the growth-promoting function of SmTCTP.